Gas sensing characteristics of novel twin-layered SnO2 nanoarray fabricated by substrate-free hydrothermal route

Novel twin-layered SnO2 well-oriented nanorods arrays have been synthesized by a substrate-free hydrothermal route of using sodium stannate and sodium hydroxide at 190 °C for 48 h. The characteristic results of the morphology and structure show that the synthesized nanoarray can be well indexed to tetragonal phase SnO2 nanorods with a diameter of 20 nm and length of several hundred nanometers. The twin-layered SnO2 nanorods array was tightly combined together by two layers of nanrods array with an apparent interface in the center. The results of the gas-sensing characteristics for various volatile organic compounds show that the sensor based on layered SnO2 nanoarray exhibits the highest gas sensitivity, very fast response and recovery to isopropanol at the operating temperature of 250 °C, and good gas-sensing performances to ethanol and acetone have also been found at the operating temperature of 278 and 300 °C, respectively. The enhanced response is attributed to the numbers of the gas transport channels increasement leading to more effective surface areas and the additional modulation of the sensor resistance due to the potential barrier at nanorod/nanorod junctions of twin-layered SnO2 well-oriented nanorods array.